A test fiber box, also commonly referred to as a “launch cord,” “launch cable,” “break-out box,” “dead zone box” or “pulse suppressor” is typically utilized in conjunction with optical test equipment to test, qualify and evaluate the transmission characteristics of optical systems, optical networks or optical equipment. Examples of transmission characteristics include loss, length, time delay and reflectance. Test fiber boxes are primarily intended to increase the length of optical waveguide between optical test equipment, such as an optical time domain reflectometer (OTDR), and a component of an optical network for purposes of testing and analysis. Test fiber boxes are also used for product demonstration and training purposes, system emulation, and for equipment calibration and benchmarking. In certain circumstances, test fiber boxes have also been employed in conjunction with an optical power meter and optical light source, or related test equipment, as a jumper for loss testing. However, the use of a conventional test fiber box as a jumper is considered impractical due to weight, bulk, and cost considerations.
One conventional test fiber box includes a length of optical waveguide suitable for use with an OTDR to test the optical time domain reflectometry characteristics of an optical network. The length of optical waveguide necessary for OTDR testing typically ranges from about 50 meters to about 5 kilometers, and the optical waveguide typically consists of a central length of unjacketed optical fiber and shorter end lengths of jacketed optical fiber. The central length of unjacketed optical fiber is substantially longer than the end lengths of jacketed optical fiber. The optical waveguide can be continuous, or the end lengths of jacketed optical fiber can be fused to the central length of unjacketed optical fiber. Regardless, the optical waveguide is stored in a rigid enclosure with the central length of unjacketed optical fiber being inaccessible to the user and the end lengths of jacketed optical fiber being accessible to the user. The unjacketed optical fiber is typically stored in a separate compartment and the end lengths of jacketed optical fiber are typically wrapped together around two or more retaining posts to form loops of jacketed optical fiber within the enclosure. The jacketed optical fiber can be unwrapped to connect the optical test equipment (i.e., OTDR) to the optical network. The dimensions of the enclosure are typically about 9 inches×8 inches×3.5 inches for a length of optical waveguide between about 50 meters and about 5 kilometers.
The size and weight of conventional test fiber boxes, however, presents several problems. The test fiber box is generally too large to fit comfortably inside an OTDR transit case and must be transported separately, resulting in possible loss or misplacement of the test fiber box. If dropped or inadvertently moved, the weight of the test fiber box can cause damage to the OTDR, to the connector adapter in the optical network, or to the components of the test fiber box itself. Furthermore, field installers and technicians naturally tend to prefer smaller, lightweight test equipment, if only to reduce the bulk of their portable tools. Another problem with existing test fiber boxes is that the jacketed optical fiber and the optical connectors on the ends of the jacketed optical fiber are difficult to manage. The end lengths of jacketed optical fiber can easily become entangled as they are repeatedly unwrapped and rewrapped, thereby causing stress and damage to the optical waveguide (e.g., glass fiber) and jacket. In addition, the test fiber box may include a protective lid, which may be inadvertently closed and thereby damage the jacketed optical fiber or connectors. Furthermore, protective caps (e.g., dust caps) for the optical connectors are easily misplaced, thereby subjecting the connectors to possible damage from dust, dirt or debris.
Although existing test fiber boxes provide for storage of the optical waveguide and connectors, that is not their primary purpose. Fiber optic storage reels are available to store excess lengths of optical waveguide in optical network enclosures, such as splice trays, distribution boxes, cross-connect cabinets, and splice closures. However, fiber optic storage reels are primarily intended for storing relatively short lengths of slack optical waveguide. Fiber optic storage reels are also available in which the optical waveguide is coiled on the reel in such a manner that the ends of the optical waveguide can be unwound from the reel at the same time and in the same direction. One such fiber optic storage reel includes an S-shaped or teardrop-shaped channel that receives the optical waveguide and reverses the direction of travel of one end, while maintaining the minimum bend radius of the optical waveguide. However, test fiber boxes typically employ relatively long lengths of unjacketed optical fiber to provide sufficient delay time for test signals to propagate. The known fiber optic storage reels do not provide adequate means for protecting and storing the long length of optical waveguide necessary for a test fiber box within a manageable size assembly.